This application claims the priority of German Patent Application Serial No. 101 28 198.6, filed Jun. 11, 2001, pursuant to 35 U.S.C. 119(a)-(d), the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a side impact beam, and in particular to a side impact beam for reinforcing a door of a motor vehicle.
Side impact beams of this type have normally a trapezoidal cross section with a central web and two flanks diverging laterally outwardly from the web and having extremities which terminate in flanges that project laterally outwardly. Depending on stiffness and energy deformation requirements and available installation space, the side impact beam may also have two profiles in side-by-side disposition (double hat profile).
Various approaches have been pursued to optimize the deformation capability of the side impact beams while reducing the material consumption. Reference is made here, for example, to U.S. Pat. No. 4,796,946 or German publications DE 693 09 699 T2 and DE 296 20 079 U1. German publication 296 20 079 U1 describes a side impact beam on two supports, whereas the disclosure of German publication DE 693 09 699 T2 is limited to a partial area of a side impact beam and not concerned with the installation space in the side wall of a motor vehicle.
It would be desirable and advantageous to provide an improved side impact beam with minimum material use and optimal energy deformation ability under consideration of available installation space.
It would also be desirable and advantageous to provide an improved method of making a side impact beam to minimize the material consumption while still optimizing the energy deformation ability.
According to one aspect of the present invention, a semi-finished flat blank is used as base material for making a side impact beam to be integrated in a motor vehicle and including at least one elongated bar, which has a trapezoidal cross section and terminates on both ends in ramp-like portions, wherein the elongated bar has a central web, flanks diverging outwardly from the central web and having extremities, and flanges connected to the extremities, and terminal attachment zones, wherein the blank is cut to size of a material band of constant thickness and includes an elongated center portion of constant width and a length portion which is sized at least half a length of the blank, wherein the center portion terminates on opposite ends in tongue-shaped end portions.
Starting material for the flat blank may be a material band of sheet metal which is reeled off a coil and has a constant sheet thickness. The material band is then cut to size, e.g., by stamping, to provide the flat blank, under the particular provision that the constant width in the elongated midsection does not produce any material loss. Only the tongue-shaped end zones, which ultimately form the attachment zone of the finished side impact beam, result in a material loss which, however, can be kept to negligible level, when suitably shaping the attachment zone.
The constant width in the elongated midsection of the blank enables consideration of the available installation space as well as the particular deformation requirements during shaping process into a side impact beam. For example, when demanding different heights of the flanks of the side impact beams from the central area in direction of the terminal attachment zone, this can be easily realized by respectively shaping the blank in such a manner that excess material, at slighter height, is displaced into the flanges and/or lateral webs, which may, optionally, be provided. Also, when the central web of the side impact beam should have a varying width, excess material can be displaced especially into the flanks and/or flanges and/or, optional, side webs.
According to another aspect of the present invention, a side impact beam for integration in a sidewall of a motor vehicle, includes an elongated bar defined by a length and having a generally trapezoidal cross section, wherein the bar includes a central length portion, which extends at least over half the length of the bar and terminates, for ensuring stiffness, on opposite ends in ramp-like end portions which taper off in terminal attachment zones for local securement, wherein the bar is comprised of a central web and two flanks diverging laterally outwardly from the central web and having extremities for connection to flanges which project outwardly in transverse direction.
In accordance with the present invention, the central length portion extends thus over half the length of the side impact beam. Moreover, the central web of trapezoidal cross section of the elongated bar has, preferably, a same width over the entire length of the elongated bar, i.e. over the central length portion and over the terminal attachment zone. In this way, the flanks, diverging laterally outwardly from the central web, can be sized over the central length portion of same height or, optionally, different height, depending on the desired energy deformation capability and available installation space. Conceivable is also a varying width of the central web.
According to another feature of the present invention, the central web may terminate in the attachment zones immediately adjacent to the end faces of the attachment zones.
According to another feature of the present invention, the flanges may end in extremities for connection to lateral webs.
For manufacturing reasons, all transitions from the central web to the flanks, from the flanks to the flanges, and from the flanges to the lateral webs may be rounded. In order to attain an optimum deformation characteristics especially in the central length portion of the side impact beam in relation to the impact point of a test body during static door crushing test according to FMVSS 214, the radii from the central web to the flanks, at least in mid-section of the central length portion, are greater than 10 mm, maximal 20 mm. Tests have shown, that a length of 100 mm is adequate to sufficiently comply with requirements of the door crushing test.